The present invention relates to molecular glass photoresists containing fluoroalcohol functionalities.
As the minimum critical dimension continues to shrink to less than 50 nanometers (nm), it is becoming increasingly difficult to simultaneously meet critical performance criteria, sensitivity, resolution, and line edge roughness (LER). The size of polymers typically employed in chemical amplification photoresists is beginning to influence performance at these dimensions. For example, it is believed that the magnitude of line edge roughness is directly correlated to the molecular weight of the base polymer in the photoresist. As a result, a number of photoresists based on low molecular weight polymers or non-polymers have been proposed to address the performance issues needed for these advanced design rules.
Molecular glass resists have gained attention as a potential candidate for next generation resist materials. Such small molecules termed “molecular glasses” (MGs) possess structural features that inhibit crystallization and display relatively high glass transition temperatures (Tg) despite their modest size. MGs combine characteristic properties of small molecules such as high purity and well defined structure with beneficial aspects of polymers such as high thermal stability and thin film forming properties. The small molecular size of 1 to 2 nanometers (nm) is expected to facilitate high-resolution patterning due to the possibility of reducing the “pixel” size of the basic imaging unit.
This new class of resist materials has shown progress in terms of resolution, sensitivity and LER. However, although MGs offer potential advantages over polymeric resists in terms of molecular size, there are many challenges with the synthesis and processing of these materials. One of the main issues with these materials is the poor solubility in a casting solvent that prevents the formation of good quality thin films. Another challenge is the ability to synthesize monodisperse materials. In previously published systems, a molecular glass resist consisted of a matrix with a core structure that is functionalized with an average number of acid labile protecting groups. These resist materials have a distribution of protecting groups. Chromatography based purification methods were used to obtain monodisperse units which showed superior performance compared to the disperse matrix. In order to obtain a monodisperse material that showed improved performance required very tedious synthetic and purification processes. Another issue is that several MG systems require diluted developer due to their high dissolution rates and therefore incompatible with 0.26N tetramethylammonium hydroxide (TMAH), the conventional developer.
Therefore to advance this resist platform, there is a need to develop molecular glass materials that are monodisperse, readily soluble in casting solvents, compatible with 0.26N TMAH developer, and easy to synthesize.